Effects Of Short-time Exposure Research Articles

Effects of short-time exposure of surface pre-reacted glass-ionomer eluate on dental microcosm biofilm

This study evaluated the antibacterial effects of short-time exposure of surface pre-reacted glass-ionomer (S-PRG) eluate on oral microcosm biofilm. Biofilms were treated with an S-PRG eluate at different concentrations (25%, 50%, and 100%), distilled water (DW), and 0.1% chlorhexidine (CHX) twice a day for 5 min repeatedly. After 7 days, the total and aciduric bacterial counts and biofilm dry weights were measured. An image analysis program calculated the red/green (R/G) ratios in the biofilm autofluorescence images. Microscopic analyses quantified the biofilm thickness and live/dead cell ratio and determined morphological changes in the biofilm. Bacterial counts and dry weights were not significantly different in the DW group for all S-PRG eluate concentrations. An increasing trend in the R/G ratio for 7 days biofilm treatment was observed for the S-PRG eluate and the DW groups. Furthermore, the live/dead cell ratios in the biofilm and the biofilm thickness of the S-PRG eluate groups were similar to those of the DW group. The bacteria morphology inside the biofilm changed only in the CHX group. Short-time S-PRG eluate treatment showed no significant antibacterial and antibiofilm effects. These results indicated that limited biofilm formation inhibition can be obtained by using only the S-PRG eluate.

Effect of Short Time Exposure to Pesticides on the Respiratory Function of the Cotton Farmers in Banikoara, Benin

Effect of Short Time Exposure to Pesticides on the Respiratory Function of the Cotton Farmers in Banikoara, Benin

Effects of short-time exposure to atrazine on miRNA expression profiles in the gonad of common carp (Cyprinus carpio)

BackgroundAtrazine is widely used in agriculture and is a known endocrine disrupting chemical. Atrazine can seep into the water body through surface, posing a potential threat to the aquatic ecological environment and human drinking water source. In vertebrate, studies have shown that it can affect reproduction and development seriously, but its molecular mechanism for aquatic animals is unknown. Aquaculture is very common in China, especially common carp, whose females grow faster than males. However, the effects of atrazine on the reproduction of carp, especially miRNA, have not been investigated.ResultsIn this study, common carp (Cyprinus carpio) at two key developmental stages were exposed to atrazine in vitro. Sex ratio was observed to analyze the effect of atrazine on the sex. MiRNA expression profiles were analysed to identify miRNAs related to gonad development and to reveal the atrazine mechanisms interfering with gonad differentiation. The results showed that the sex ratio was biased towards females. Atrazine exposure caused significant alteration of multiple miRNAs. Predicted targets of differently-expressed miRNAs were involved in many reproductive biology signalling pathways.ConclusionsOur results indicate that atrazine promoted the expression of female-biased genes by decreasing miRNAs in primordial gonad. In addition, our results indicate that atrazine can up-regulate aromatase expression through miRNAs, which supports the hypothesis that atrazine has endocrine-disrupting activity by altering the gene expression profile of the Hypothalamus-Pituitary-Gonad axis through its corresponding miRNAs.

Effects of short term lead exposure on gut microbiota and hepatic metabolism in adult zebrafish

Lead (Pb) is one of the most prevalent toxic, nonessential heavy metals that has been associated with a wide range of toxic effects in humans and environmental animals. Here, effects of short time exposure to 10 and 30 μg/L Pb on gut microbiota and hepatic metabolism were analyzed in adult male zebrafish. We observed that both 10 and 30 μg/L Pb increased the volume of mucus in the gut. At phylum level, the abundance of α-Proteobacteria decreased significantly and the abundance of Firmicutes increased significantly in the gut when treated with 30 μg/L Pb for 7 days. In addition, the 16S rRNA gene sequencing for V3-V4 region revealed a significant change in the richness and diversity of gut microbiota in 30 μg/L Pb exposed group. A more depth analysis, at the genus level, discovered that 52 gut microbes identified by operational taxonomic unit analysis were changed significantly in 30 μg/L Pb treated group. Based on GC/MS metabolomics analysis, a total of 41 metabolites were significantly altered in 30 μg/L Pb treatment group. These changed metabolites were mainly associated with the pathways of glucose and lipid metabolism, amino acid metabolism, nucleotide metabolism. In addition, we also confirmed that the transcription of some genes related to glycolysis and lipid metabolism, including Gk, Aco, Acc1, Fas, Apo and Dgat, decreased significantly in the liver of zebrafish when exposed to 30 μg/L Pb for 7 days. Our results observed that Pb could cause gut microbiota dysbiosis and hepatic metabolic disorder in zebrafish.

Effect of different temperatures on the fatigue behavior of interference fitted plates of Al-alloy 7075-T6

The effect of short time exposure to thermal cycle on the fatigue life of interference fitted fastener holes was evaluated by experimental and numerical method in Al-alloy 7075-T6. When interference fitted holes are subjected to temperature, the pre-stresses produced by interference fit may be considerably redistributed. To investigate the pre-stresses redistribution and its effect on the fatigue life of interference fitted specimens, two different temperatures (i.e. 60 ℃ and 120 ℃), apart from room temperature, were selected. The fatigue tests were performed to obtain S–N curves. Tangential pre-stress distribution was analyzed by the finite element method. Three-dimensional stress distributions of interference fit process have been determined around the hole at three temperatures: 25 ℃, 60 ℃, and 120 ℃. The finite element analyses justify the experimentally observed fatigue test behavior. The results show that the short period thermal cycle could improve the fatigue life of the prepared samples.

An experimental investigation on the effect of short time exposure to elevated temperature on fatigue life of cold expanded fastener holes

An experimental study has been carried out to investigate the effect of short time exposure to elevated temperature on fatigue life of cold expanded fastener holes. When cold expanded holes are subjected to temperature variations their fatigue life changes remarkably. However the exact governing mechanism has not been clearly addressed before. In this study, another stress relaxation mechanism rather than creep has been introduced which happens at a short time due to temperature rise. Results of fatigue tests on Al 7075-T6 show that the effect of this mechanism can be beneficial or detrimental. This research has sought to clarify this issue.

Heavy Metal Effects on the Metabolic Activity of Elliptio complanata: A Calorimetric Method

AbstractThe effects of short time exposure to mercury (Hg2+), cadmium (Cd2+), and copper (Cu2+) ions on the metabolic activity of gill tissue from the freshwater bivalve Elliptio complanata were investigated by isothermal calorimetry and respirometry. Metabolic heat rates were altered following exposure of gill tissue to these ions over the concentration range from 10−6 to 10−3 M. The effects of metal ions on metabolic heat rates were metal ion specific and time and concentration dependent. Treatment of tissue with low concentrations of Hg2+ and Cu2+ for short times caused stimulation of metabolic heat rates. Longer exposures and higher concentrations caused inhibition. Cadmium was inhibitory under all conditions tested. Treatment of mitochondria isolated from gill and muscle tissues showed a similar pattern of stimulation of respiratory rate at low concentration and inhibition at higher concentration. Analysis of CO2, and O2 from the headspace gasses in the calorimeter ampule showed an enhancement of respiratory quotient (RQ, i.e., RCO2/RO2 where R = rate) following addition of 10−3 M Cd2+ for 30 min. The microcalorimetric method proved to be a useful technique to assess toxicity of heavy metals on the gills of a freshwater bivalve.

Effects of Cigarette Smoke and Nicotine on Duodenal Bicarbonate Secretion in the Rabbit and the Rat

The effects of short-time exposure to cigarette smoke on duodenal mucosal bicarbonate secretion were studied in anesthetized rabbits and rats. The bicarbonate secretion was measured by continuous titration of recirculating luminal perfusate. In artificially ventilated rabbits, intermittent exposure to cigarette smoke during two 10-min periods caused a marked (approximately 40%) decrease (p less than 0.01) in duodenal bicarbonate secretion. After the exposures, secretion gradually recovered and had returned to the pre-exposure rate after 50 min. The decrease in secretion was associated with decreases in heart rate (approximately 15%) and blood pressure (approximately 30%) that, however, were of shorter duration. Neither reduced amounts of smoke (1/6 or 1/3) nor nicotine (25-1,000 micrograms/kg, intravenously) had any major effect on the bicarbonate secretion. In the spontaneously breathing rat, smoke was administered for 1-2 breaths every 30 s during a 5-min period. This exposure resulted in a significant (p less than 0.05) decrease in bicarbonate secretion and some increase in the blood pressure. Exposure to smoke had no effect on the secretion in rats with both splanchnic nerves cut, suggesting neural sympathetic mediation of the smoke-induced inhibition.

Effects of short-time exposure to naphthalene, methyl-, and hydroxynaphthalenes on two different embryonic stages of cod (Gadus morhuaL.)

Abstract The toxicity of 3 ppm of five naphthalene derivatives on newly fertilized cod eggs was ranked according to increasing toxicity as follows: naphthalene, 2-naphthol, I-naphthol, 2- methylnaphthalene, and 1,3-dimethylnaphthalene. For eggs exposed just prior to hatching the ranking of the toxicity of the test substances was different, viz. naphthalene, 2-methylnaphthalene, 1-naphthol, and 1,3-dimethylnaphthalene/2-naphthol. Effects such as delayed cell division, abnormal development, changes in hatching rate, and reduced survival of the embryo were recorded. Quantiative analyses of the test substances were made using UV-spectroscopy for naphthalene/methylnaphthalenes and fluorometry for naphthols.